Changelog checker should not treat `package.json` as changed if it only has changes to `devDependencies`

[mcmire]

If the only changes in a monorepo package's package.json is to the devDependencies, then the changelog checker should not ask the release author to document the change in the changelog.

This is important to ensure that we do not mistakenly train people to add no-changelog when they encounter problems.

As an example: MetaMask/core#5978 (comment)